Omegas, iron, and vitamin D, oh my! Advice on supplements can be conflicting and overwhelming for women of a certain age—particularly when it comes to calcium. That’s especially true now, with the release of a study showing that too much of the mineral may actually double a woman’s risk of death by cardiovascular disease.
For the study, published February 13 in the British Medical Journal, a team from Uppsala University in Sweden analyzed self-reported data from 61,443 women over the course of 19 years. During that time, nearly 12,000 women died, the majority from cardiovascular disease.
The highest rates of death, overall, were among women whose calcium intake was higher than 1,400 mg a day (from supplements or a combination of food and supplements, though not from food alone); those women were twice as likely to die than women getting between 600 and 999 mg. But those at the other end of the scale—getting less than 600 mg of calcium a day—also had an increased risk of death.
“Calcium is an essential mineral needed in all cells of the body,” lead researcher Karl Michaëlsson told Yahoo! Shine. Though the study didn’t look into the reasons behind the findings, Michaëlsson speculates that the body might absorb high intakes of calcium too quickly, thus throwing off the balance of hormones and vitamin D.
The Mayo Clinic’s Dr. Bart Clarke, a member of the American Society for Bone and Mineral Research, described the risk of too much calcium to Shine this way: “The bones can’t make use of it fast enough, and then it finds storage in places you don’t want it, such as in the cardiovascular system, or in the urine, which can lead to kidney stones.” Calcium seems to be absorbed too quickly especially in the form of supplements, he said.
The BMJ study is not the first to make connections between high calcium intakes and an increased risk of death. A 2010 meta-analysis of data in New Zealand showed that adults taking at least 500 mg supplements of calcium a day increased their risk of heart attack by 30 percent. Another, published in the journal Heart in 2012, showed that people who got their calcium almost exclusively from supplements were more than twice as likely to have a heart attack than those who didn’t take supplements.
Clarke was careful to note that data-gathering studies like this one—which relied on subjects self reporting and isolated the effects of calcium without taking vitamin-D intake into account—are best thought of as suggestive, rather than definitive. To really get answers, he said, a controlled study is needed. “But that would be very expensive,” he noted, “and nobody wants to fund it.”
The estimated average intake for people ages 20 to 90 is just 500 to 700 mg daily, according the CDC’s National Health and Nutrition Examination Survey. But currently, the Institute of Medicine, which advises nutrient intake based on scientific data, recommends 1,000 to 1,300 mg a day for most children and adults. So what’s the best way for women to protect their bones and their hearts and cardiovascular systems?
“Calcium in the form of diet doesn’t seem to be of increased risk,” Clarke said. For that reason, he suggests sticking to the IOM’s intake recommendations, but mainly with food. Cheese, yogurt, broccoli, almonds, tofu, sardines, kale and other leafy greens are all good forms of dietary calcium. Vitamin D is important to help your body absorb the calcium, so be sure to get your levels tested. And, beyond eating well, supplementing to keep your intake levels up, long as you don’t go over the recommended allowance, would probably be a good idea, Clarke said.